The present invention relates to electrical actuators useful in washing machines and the like, and in particular to an actuator that provides for rapid initial engagement with delayed release.
Electrical actuators that rapidly engage upon receipt of an actuation signal, but that delay releasing when the actuation signal ceases may be used, for example, in a lid lock on a clothes washing machine. With such an actuator, the lid locks quickly upon the start of the spin cycle and remains locked for a period of time after the spin cycle ends to allow the spin basket to coast to a stop before the lid can be opened. Desirably, the electrical actuator should provide a slow release not only when the actuation signal ends, but in the event of unexpected power loss.
Bi-metallic actuators, known in the art, can provide a slow release, either at the end of an actuation signal (heating the bi-metal) or upon power failure, as the bi-metal element cools. However, the same thermal mechanism that slows the cooling of the bi-metal also delays its heating undesirably delaying the engagement of the actuator.
U.S. Pat. No. 5,823,017, assigned to the assignee of the present invention and hereby incorporated by reference, describes an electromagnetic actuator that may be actuated rapidly and which is bi-stable so as to retain actuation even in the absence of power. An associated timing circuit provides for a delayed release of the actuator upon cessation of the actuation signal. An energy storage capacitor allows operation of the timer circuit even in the absence of power.